In modern high speed/high quality electrostatographic reproduction apparatus (copier/duplicators or printers), a latent image charge pattern is formed on a uniformly charged dielectric support member or primary image-forming member (PIFM). Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the support as a toner image. The dielectric support is then brought into contact with a receiver member and an electric field applied to transfer the marking particle developed toner image to the receiver member from the dielectric support. After transfer, the receiver member bearing the transferred toner image is transported away from the dielectric support and the toner image is fixed to the receiver member by heat and/or pressure to form a permanent reproduction thereon. The receiver member is a paper or plastic transparency sheet upon which the image is to be fixed.
An alternate approach is to use an intermediate transfer member (ITM) and to transfer the toner image formed on the PIFM to the ITM and then to the receiver member. Thus, immediately before transfer of a toner image to a receiver member the toner image may either be on a PIFM or an ITM, either of which is a toner image bearing member (TIBM).
In order to transfer the toner image on the TIBM to the receiver member it is known to transport the receiver member through a transfer nip using a paper transport web. During transfer both the receiver member and the paper transport web are disposed in an electric field to urge transfer of the toner particles on the TIBM to the receiver member.
Heretofore, the paper transport web might be either a seamless belt or a belt with a seam. Seamed belts are preferred because for larger belts they are generally less expensive. The seaming technologies commonly used in the manufacturing of paper transport webs are ultrasonically-welded lap joints, adhesive lap joints, and adhesive butt joints. Each of these seams is considered a hindrance to toner transfer because of a capacitive change introduced in the transport web at the seam. A capacitive change due to the increase in thickness of the transport web at the seam, the presence of adhesive with mismatched dielectric properties, or the presence of an air gap, due to the thickness change in the web, trapped between the receiver and the paper transport web influence the electric field at the seam, causing a change in density of toner transferred to the receiver. An observer can easily detect this image artifact. As noted in U.S. Pat. No. 5,487,707, the seam constitutes a nonfunctional area of a belt and "does not participate in belt functionality such as the formation and transfer of a toner or developer image". Thus, it is suggested in this reference that the non-functional part of the belt; i.e. the seam be kept relatively small from about 1 mm to about 3 mm wide. Since the seam is considered in the prior art nonfunctional for transfer purposes the seamless belts are preferred where cost is not an issue. Where the cost of a seamless belt is considerably more than that of a belt formed with a seam, a belt with a seam is used and accommodation is made through timing controls to ensure that the receiver member is not positioned over the seam area. A problem with this is that where multiple color stations are provided for simultaneous transfer of color toner images to plural receiver members productivity can be reduced because a transfer may need to be delayed to avoid feeding of a receiver member over a seam area.
It is therefore an object of the invention to overcome the deficiencies in the prior art and to provide a reproduction apparatus and method characterized by a seamed paper transfer support belt that can be used as if it were seamless.
It is another object of the invention to provide a belt having a seam and used as an ITM and wherein images are periodically formed on the belt and allowance is made for images to be presented over the seamed area of the belt prior to transfer of an image to a receiver member.